Adding Tenant to Existing Lease

[Blake C.]

I had tenanted that moved in a week and a half ago. Its a young couple that have now decided that they want the girls brother to come and live with them to help share the rent and give him a place to stay. All are over the age of 18 and will be paying rent. The original guy and girl are on the lease together.

Whats the proper way to handle adding the third party? Thanks for the advice from those who have been there before.